>Has anyone ever done something in .NET to create new site entries in IIS? I am looking for something that will allow me to add from my application a new entry in IIS for a Web site by specifying the home directory, the application pool, the IP used, the type of scripting and the .NET Framework version that has to be used.

You don't say what version of IIS.
For IIS 7.0 check the Microsoft.Web.Administration namespace:
http://msdn.microsoft.com/en-us/library/microsoft.web.administration.aspx
Some simple examples here:http://learn.iis.net/page.aspx/165/how-to-use-microsoftwebadministration/

If it's an earlier version there are a few options:
http://msdn.microsoft.com/en-us/library/ms525885.aspx
http://msdn.microsoft.com/en-us/library/ms524505.aspx